Ligand-dependent formation of ion-pair Cu/Cu trifluoromethyl complexes containing bisphosphines.

We report novel ion-pair bisphosphine Cu/Cu trifluoromethyl complexes [(P)Cu][Cu(CF)] (P = DPPE, BINAP or Xantphos) featuring tetrahedral Cu and square planar Cu units that are prepared via oxidative trifluoromethylation of CuI with CFSiMe in the presence of AgF. The bisphosphine Cu/Cu CF complexes are highly reactive for aerobic trifluoromethylation of arylboronic acids to produce trifluoromethylated arenes in good to quantitative yields, which is in sharp contrast to the Cu/Cu complex with phen/PPh ligands (1'). These results not only provide strong evidence that both the neutral and ion-pair Cu CF complexes are competent catalytic species for Cu-mediated oxidative trifluoromethylation reactions, but also have important mechanistic implications that the active catalyst and reaction mechanism should be distinct and ligand-dependent for trifluoromethylation reactions with different types of ancillary ligands.